Beverage preparation machines are well known in the food science and consumer goods area. Such machines allow a consumer to prepare at home a given type of beverage, for instance a coffee-based beverage, e.g. an espresso or a brew-like coffee cup.
Today, most beverage preparation machines for in-home beverage preparation comprise a system made of a machine which can accommodate portioned ingredients for the preparation of the beverage. Such portions can be soft pods or pads, or sachets, but more and more systems use semi-rigid or rigid portions such as rigid pods or capsules. In the following, it will be considered that the beverage machine of the invention is a beverage preparation machine working with a rigid or semi-rigid capsule.
The machine comprises a receptacle or cavity for accommodating said capsule and a fluid injection system for injecting a fluid, preferably water, under pressure into the capsule. Water injected under pressure in the capsule, for the preparation of a coffee beverage according to the present invention, is preferably hot, that is to say at a temperature above 70° C. However, in some particular instances, it might also be at ambient temperature, or even chilled. The pressure inside the capsule chamber during extraction and/or dissolution of the capsule contents is typically about 1 to about 8 bar for dissolution products and about 2 to about 12 bar for extraction of roast and ground coffee. Such a preparation process differs a lot from the so-called “brewing” process of beverage preparation—particularly for tea and coffee, in that brewing involves a long time of infusion of the ingredient by a fluid (e.g. hot water), whereas the beverage preparation process allows a consumer to prepare a beverage, for instance coffee, within a few seconds.
The principle of extracting and/or dissolving the contents of a closed capsule under pressure is known, and consists typically of inserting the capsule in a receptacle or cavity of a machine, injecting a quantity of pressurized water into the capsule, generally after piercing a face of the capsule with a piercing injection element such as a fluid injection needle mounted on the machine, so as to create a pressurized environment inside the capsule either to extract the substance or dissolve it, and then release the extracted substance or the dissolved substance through the capsule. Capsules allowing the application of this principle have already been described for example in applicant's European patents No. EP 1472156 B1, and EP 1784344 B1.
Machines allowing the application of this principle have already been described for example in patents CH 605 293 and EP 242 556. According to these documents, the machine comprises a receptacle or cavity for the capsule and a perforation and injection element made in the form of a hollow needle comprising in its distal region one or more liquid injection orifices. The needle has a dual function in that it opens the top portion of the capsule on the one hand, and that it forms the water inlet channel into the capsule on the other hand.
The machine further comprises a fluid tank—in most cases this fluid is water—for storing the fluid that is used to dissolve and/or infuse and/or extract under pressure the ingredient(s) contained in the capsule. The machine comprises a heating element such as a boiler or a heat exchanger, which is able to warm up the water used therein to working temperatures (classically temperatures up to 80-90° C.). Finally, the machine comprises a pump element for circulating the water from the tank to the capsule, optionally though the heating element. The way the water circulates within the machine is e.g. selected via a selecting valve means, such as for instance a peristaltic valve of the type described in applicant's European patent application EP 2162653 A1.
When the beverage to be prepared is coffee, one interesting way to prepare the coffee is to provide the consumer with a capsule containing roast and ground coffee powder, which is to be extracted with hot water injected therein.
In many instances, the machine comprises a capsule holder for holding a capsule, which is intended to be inserted in and removed from a corresponding cavity or receptacle of the machine. When a capsule holder is loaded with a capsule and inserted within the machine in a functional manner, the water injection means of the machine can fluidly connect to the capsule to inject water therein for a food preparation, as described above. A capsule holder was described for example in applicant's European patent EP 1967100 B1.
Capsules have been developed for such an application of food preparation, and in particular for beverage preparation, which are described and claimed in applicant's European patent EP 1784344 B1, or in European patent application EP 2062831.
In short, such capsules comprise typically:                a hollow body and an injection wall which is impermeable to liquids and to air and which is attached to the body and adapted to be punctured by e.g. an injection needle of the machine,        a chamber containing a bed of roast and ground coffee to be extracted, or a soluble ingredient or mix of soluble ingredients,        an aluminium membrane disposed at the bottom end of the capsule, closing the capsule, for retaining the internal pressure in the chamber.        
The aluminium membrane is designed for being pierced with piercing means that are either integral with the capsule, or located outside of said capsule, for example within a capsule holder of the machine.
In the field of the present invention, it is considered that the piercing means is located outside of the capsule, for instance the piercing means is integrated to a capsule holder.
Usually, the piercing means is a plate having a substantially disc-shaped surface covered with piercing elements such as small pyramids or spikes, adapted in shape and size to pierce through the bottom membrane of the capsule when the latter is bent due to internal fluid pressure building-up within the capsule. Beyond the piercing effect, the piercing means also has a function of support of the bottom membrane, and ensures that the latter does not bend too much when subject to internal pressure within the capsule. It therefore prevents that the bottom membrane is completely torn open by the pressure. This would be particularly undesirable, since a wide opening through the membrane could allow ingredient material (e.g. roast and ground coffee) to pass through, and fall into the consumer cup, which would result in beverage contamination giving very poor in-cup product quality. The opening of the bottom membrane by the piercing means is therefore the result of a balanced mechanical effect, providing small openings through the membrane, which are due to action of the piercing elements, while the same piercing means prevents wide opening, bursting, or similarly wide tearing of the same bottom membrane.
As described and illustrated in the prior art publications, for instance in EP 1472156 B1, the surface of the piercing means—which in the cited prior art is a piercing plate—substantially corresponds to the surface of the capsule pierceable bottom membrane.
In some instances though, particularly when the beverage machine is made compatible with several capsule types, the piercing means can be designed such that its surface does not correspond to the entire surface of the bottom membrane. For example, the centre of the piercing means can be made hollow, and the piercing elements are distributed across a ring-shaped area rather than a disc-shaped area.
In such instances when the surface of the piercing means does not correspond to the surface of the capsule pierceable bottom membrane, the latter can burst or be torn before the appropriate pressure is reached within the capsule.
Capsule bursting can be such that a too wide opening is created through the bottom membrane of said capsule, through which some non-consumable ingredient e.g. coffee particles, can escape and flow into the cup, which is of course highly undesirable, as it results in a messy product dispensing, and poor quality of the resulting product in cup (e.g. mix of liquid coffee with solid coffee particles). This is especially the case if the piercing means of the machine comprise a zone which is hollow, i.e. does not comprise.
Moreover, product to be prepared inside the capsule requires an appropriate pressure and temperature, in order to achieve the best texture and taste. If the bottom membrane of the capsule opens too rapidly, the adequate internal pressure within the capsule is not reached and the resulting product does not have appropriate sensory quality.
It is therefore a main objective of the invention to provide an ingredient capsule for use in a food, e.g. a beverage, preparation machine, that prevents inadequate (typically too early and/or too wide) capsule opening, and therefore to provide the best in-cup quality to the consumer, in particular when the piercing means of the machine is not specifically adapted to opening such a capsule.